An ever-expanding family of ets-related genes has been found in the human genome, as well as in that of other species. Features of this ets family include a DNA-binding domain, as well as a helix-loop-helix motif, which has been postulated to be a site for protein-protein interaction. The goal of this project is to identify proteins which interact with individual ETS proteins, and thus give rise to functional differences among the members of the ets family. We have demonstrated the existence of interacting proteins using protein blotting techniques, and have been utilizing the yeast two-hybrid system to find the genes encoding these ets-interacting proteins. ETS1, ETS2, and ERGB/FLI1 genes have been placed into shuttle vectors which express the Ets proteins fused with the yeast GAL4 DNA binding domain. We have constructed a cDNA library from human T-lymphocyte CEM cells and have been using this to screen for interacting proteins. Several clones have been obtained from screens of the CEM library with ETS1 and ERGB/FLI1, and we are in the process of testing their specificity for the target ETS protein. Specifically interacting proteins will be characterized for their regions of interaction, tissue expression, and effect on ETS- regulated genes.